The prior art contains several examples of attempts to utilize the phenomenon of bi-axial orientation in thermoplastic material for the blow molding of various articles. For example, U.S. Pat. Nos. 3,311,684; 3,470,282; 2,919,462, and 3,337,666 provide various blow molding arrangements. Generally, the prior art processes attempt to cool a parison to a uniform orientation temperature, stretch the parison and then blow the stretched parison into a container. Alternatively, other proposals involve the injection molding of a parison, the cooling and the reheating of the injections molded parison, and the blowing of the reheated parison to its final configuration.
Such processes and the apparatus for implementing these processes are ill adapted to high production rates. Furthermore, such processes are not adaptable to conventional, free extrusion blow molding machines now in use in many blow molding operations.
In view of the very substantial advantages residing in blow molding under conditions conductive to bi-axial orientation, there does exist a need for a practical, rapid, efficient blow molding apparatus which is adaptable to the over-all free extrusion blow molding technique. If such apparatus would, at the same time, eliminate extraneous flash from the article, e. g., at the neck, handle and bottom portions of a bottle, a long standing need in the art would be satisfied.